I mean, flashback to 2010 ... zones, dtrace, smf, iscsi and zfs were very well integrated together and lightyears beyond what was available in the Linux space at the time.

Zones were lightweight, more akin to the Linux vserver project or lxc. You could make a zone on its own zfs filesystem, clone the zone (which creates a zfs clone), launch the clone, run a throw-away task, tear the zone down which also discards the zfs snapshot+clone. It was quick and cheap but also half a decade before Docker was released or popularized.

zfs integrated into other parts of the system just as well. eg: iSCSI volumes backed by a zpool and export properties configured in zfs. All of these technologies were built with the idea of being "self-healing." Meanwhile, Linux has a disparate iSCSI daemon, lvm+ext4/reiserfs, initd, and probably 20 different tools to learn if you want to grab metrics across the stack like dtrace on Solaris was capable of.

The out of band management was amazing too. Yes, some x86 hardware had ilom but like everything else in the space, it's bolted on and not truly integrated.

Sun made really nice stuff that outpaced Linux in a lot of ways. The ecosystem came from a time of competing BSDs and looked for paying customers for the engineering marvel they had created. They were used to customers figuring out how to use Unix, and the Linux crowd at the time still fit that rubric. The OS was not optimized for low-latency terminal interaction and thus "felt slow" (aka: Slowaris) but a well tuned DB on Sparc really cooked.

Finally, I went to a few Sun events and had Sun reps come and look at what we were doing. They were definitely happy to help with any kind of outreach/onboarding we needed. The issue was none of "onboarding" but was a lot of "Linux is a movement." In early times, Linux was an anti-corporate movement and some of that energy carried through to the 2010s. It's sadly ironic because Sun itself has roots in open standards and an anti-establishment mentality.